Pressure fluid control system and valve



Sept. 2"(', 1960 R. D. KREHB IEL PRESSURE FLUID CONTROL SYSTEM AND VALVE- Filed June 25, 1959 7 mm m Q a i mm w mm mm I 2 H. 1. 1 II I x J 2 l P I m Q 45m x /7 77 4 f A/ mm RQQK Q 5w 3 mm t S A\om I ATTORNEY,

United States Patent PRESSURE FLUID CONTROL SYSTEM AND VALVE Filed June 25, 1959, Ser. No. 822,905

6 Claims. (Cl. 121-465) This invention relates to a system for controlling and co-ordinating the movements of a pair of opposed coacting hydraulic motors, whether or not the major components of the system are grouped in a single housing, as well as to a unitary valve in which the essential com ponents of the control system are grouped in a single housing.

More particularly my invention relates to a system and valve for controlling a hydraulic motor actuated mechanism, such as may be used for swinging the boom of a mechanical shovel in either direction about a vertical axis. One boom actuating mechanism which my inven- 2 description is read in connection with the accompanying drawing.

The single drawing figure is a schematic view of a hydraulic motor actuated mechanism for swinging the boom of a power shovel about a vertical axis, my invention being illustrated as embodied in a unitary control valve, shown in longitudinal vertical central section, for controlling such mechanism.

While the valve shown in the drawing is specifically designed for cooperative association with other valves in a multiple valve bank, and consequently includes a socalled zig-zag type neutral by-pass passage 10--1'1 through which fluid may continuously flow. from the pump discharge back to the reservoir when there is no demand on the system, it will be understood by those familiar with this art that the invention described herein can be embodied in unitary valves designed to function tion is especially adapted to control is illustrated herein as including a pair of opposed single acting fluid motors or working cylinders which have their respective plungers connected to the opposite ends of a taut chain or other similar flexible element which is incapable of transmitting a compressive force, and in which the chain is operably associated intermediate itsends with a boom carrying vertical pivot so that when the chain is pulled in one direction by the plungerof one motor, the boom is swung in one direction about its pivot, and when the chain is pulled in the opposite direction by the plunger of the other motor, the boom is swung in an opposite direction.

*In such a boom actuating mechanism the boom and the load which it ordinarily carries at its outer end develop an immense amount of kinetic energy during a rapid swinging movement of the boom. Furthermore, if the rapid swinging movement of the boom and its load is stopped abruptly by the blocking of fluid flow both to and from the two actuating motors, inertia forces cause excessive pressure to build up in that cylinder from which the return of fluid to the system reservoir is blocked. Such excessive pressure causes hammer or shock throughout the hydraulic system and often causesbreakage in parts of the actuating mechanism. Furthermore, for satisfactory operation of such a boom swinging mechanism it is desirable to keep both flights of the chain taut at all times. It is further desirable to prevent cavitation in either of the actuating cylinders.

It is an important object of this invention to provide a control system and valve for such a boom swinging mechanism which is capable of quickly absorbing the kinetic energytransmitted to the motors by the swinging boom and its load, thereby cushioning the stopping of boom motion, and preventing damage to the system from excessive pressures. v

It is a further important object of the invention to prevent cavitation in either actuating cylinder by alfording a flow of auxiliary fluid to either cylinder when pressure therein drops below normal operating pressure. It is an additional object to provide a control system and valve for such a boom operating mechanism which will maintain both flights of the boom operating chain taut at all times.

Other objects and advantages of the invention, together with the details of construction of one embodiment thereof, will be more clearly understood when the following independent of any association with other valves in a multiple valve bank.

'Excepting the fluid flow control system and valve shown in the drawing, the hydraulic system and the boom swinging mechanism shown schematically. therein are considered conventional. A pump 12 is supplied with fluid from a reservoir 13 through a .conduit 14, and delivers fluid at an increased pressure through a relief valve 15 to apressure fluid passage 16 in the body 17 of the control valve.

Under selective control by a shiftable valve spool 1% pressure fluid may be delivered from the supply passage 16 through either of two circuit control passages 19' and '20, through the respective motor ports21 and 22, and connecting lines 23 and 24 to either of two single acting fluid motors 25 and 26, while fluid is simultaneously returned from the other fluid motor through its connected circuit control passage 19 or 24) into a return passage 27 and its connected return line 28, to the reservoir 13 to complete the circuit.

Generally, my invention includes afluid supply. means 16; a fluid return means 27. 28;,two circuit control passages 19 and 20 for connection respectively to actuating motors 25 and 26; a shiftable valve means which is effective in the neutral position shown to block the flow of supply fluid to both circuit control passages and .to block the flow of fluid from either of .the motors through its associated circuit control passage directly into return passage 27, and shiftable to selectively connect either circuit control passage with the supply passage while connecting the other circuit control passage directly with the fluid return passage, said shiftable valve means also being. effective in intermediate positions to block the flow of fluid from one fluid motor through its circuit control passage directly into the return passage 27, while afford:

both directions between the respective circuit control pas-.

sages 19 and 20 and the transfer passage 29; and an adijustable differential .pressure: opened check valve 32 oriented to afford flow of fluid only from the transfer passage 29 into return passage 27.

The valve illustrated, which embodies my control system, includes a housing 17 which has a longitudinal valve spool receiving bore 33, which. slidab ly receives the fluid flow control spool 18. This bore 33 is intersected by two cooperating branches l0 and 11 of a neutral pressure fluid by-pass passage, and by two separated but communicating fluid pressure supply ducts 34 and 35 .to which pressure fluid is delivered by fluid supply. passage 1, through a ball check valve 36. Bore 32 is also intersected by the two circuit control passages 19 and 20, each located adjacent a respective one of the supply ducts 34 and 35.

While check valve v32 is shown as being housed in a counter bore in spool 18, it will be understood that this check valve may be located elsewhere at any location in which it may afford flow of fluid from transfer passage 29 into return passage 27. As shown, valve 32 includes an adjustable valve seat insert 37,- the longitudinal adjustment of which varies the compression of spring 38, and thereby varies the pressure required to unseat ball 32 and allow fluid flow from the transfer passage 29 through the ports 68 and 69, into return passage 27.

Valves 30 and 31 are identical in construction. Each of these valves is in effect two separate valves, having two separate functions. The construction of this valve is the subject of a separate patent application, co-pending Serial No. 809,946, filed April 30, 1959 in the name of Marvin L. Wolf. Each valve serves as a circuit. relief valve oriented to permit the flow of. fluid under excessive pressure from its associated circuit control passage into the fluid transfer passage .29, and also serves as check valve oriented to permit the flow of fluid from the fluid transfer passage 29 into its associated circuit control passage, when the pressure therein drops below the pressure required to open check valve 32. Since the identified patent application completely discloses the construction and operation of this valve. it should be sufficient to simply describe the operation of the valve in this application. The operation of these valves will be described in connection with. the control system as a whole.

The two single acting fluid motors 25 and 26 are provided respectively with working plungers 39 and 40. The opposite ends of a chain are respectively secured to these plungers. The intermediate portion of the chain is strung over a sprocket 41 secured to rotate with an upright shaft 42 which is suitably journaled in structure 43, and which is suitably secured to a boom, not shown, so that the boom will be swung from side to side as the shaft is oscillated. A cable or any other flexible element may be used as a substitute for the chain. The two flights of the chain, one on either side of the center of pulley 41, are respectively numbered 44 and 45, for clarity in describing the operation.

To control fluid flow from the fluid supply means 16 to and from the respective fluid motors 25 and, 26, ,a shiftable valve means in the form of cannelured valve spool 18 is reciprocably mounted in the bore 33 of the, housing 17. The spool is urged toward a neutral or centered position, as shown in the drawing, by a conventional spring centering assembly designated as a'whole by the numeral 46.

The lands and grooves of spool 18 are so located that when the spool is in its neutral position, as. shown in the drawing, communication. between the fluid pressure. supply means 16 and both circuit control passages '19 and 20 is blocked. Likewise communication is blocked between both circuit control passages and the fluid return passage 27. During normal operation this spool location will normally lock. both the plungers '39 and 411 against movement toward. sprocket 41, thus holding the boom connected to shaft, 42 in a, fixed position.

Operation.

When spool 18 is moved to the left'pressure supply duct 35 is connected to circuit control passage 20 and fluid flows to motor 26'. moving plunger 40 inward in this motor. Such. movement is transmitted through sprocket 41 to boom pivot shaft 42 which is partially rotated to swing the boom clockwise. Chain flight 44' forces plunger 39 to move outward of its cylinder toward sprocket 41. This forces oil. fi'om motor 25 through line 23 into circuit controlpassage 19, the upper end of which has been connected through the spoolibore to fluid return passage 27 by the mentioned spool move- 4 ment. The returning fluid thus returns through passage 27 and line 28 to the reservoir 13.

When the boom carried by the shaft 42 has been moved to the desired position, spool 18 is returned toward its original position. As the spool returns fluid flowing from circuit control passage 19 into return passage 27 is blccked before the oil flowing from supply duct 35 into circuitcontrol passage 20 isshut off. This is due to the relative locations of the shoulders 47 and 48 on .the spool. In this intermediate spool position, chain flight 45 is kept tau-t by fluid pressure on plunger 40 and chain flight 44 is kept taut by fluid trapped in the motor cylinder and in the circuit control passage 19.

If the inertia force in the swinging boom is high, this force will be transmitted to shaft-42 and its sprocket 41, which will tend to move plunger 39 further outward of its cylinder, forcing oil out, and raising the pressure in circuit control passage 19. When the pressure in circuit control passage 19 exceeds the setting of the relief valve portion of valve 30, fluid will flow from circuit control passage 19 through orifice 49, will unseat pilot valve 50, and flow through outet 51 and ports 52 into fluid transfer passage 29, thence through ports 68, lifting ball 32 off its seat against the pressure of spring 38, and into return passage 27 and to the reser- V011. gins the pressures in circuit control passage 19 and in relief valve chambers 53 and 54 are equal. The fluid in chamber 53 acts on the full area of the end of the main valve body 56, while the fluid in chamber 54 can act only on that area of the valve body 56 which is not covered by valve seat 57. Since the areas of the valve body acted on are unequal, the total forces exerted in opposite directions on valve body 56 are unequal, and the body is normally urged toward its seat by the larger force exerted by the fluid pressure in chamber 53.

However, when pilot valve 50 is unseated and fluid begins to flow from chamber 53, fluid flow through orifice 49 causes a decided drop in pressure in chamber 53. Due to this drop in pressure the force exerted on the valve body 56 in a valve opening direction (to the right in valve 30) by the pressure fluid in chamber 54 soon exceeds the total force exerted in a valve closing direction by the spring 59 and by the lower pressure fluid in chamber 53. When such an unbalanced condition is reached the main valve body 56 moves away from. itsv seat 57, and fluid flows from the motor 25 through circuit control passage 19 through ports 60 and valve seat 57 into fluid transfer passage 29, to relieve the pressure in the fluid motor 25 caused by the inertia forces in the boom and its load. The action of valve 30, thus described, serves as a hydraulic cushion to absorb the kinetic energy developed by the boom during its. swinging movement. Such absorption prevents the build up of extreme pressure in circuit control passage 19 and prevents hammer throughout the entire hydraulic system. It also prevents the placing of excessive strain on any part of the mechanical portion of the system. Allthe above described action occurs while the spool 18 is in the specified intermediate position. As the.

spool 18 continues to travel towards its neutral position, as shown in the drawing, the flow of oil from supply duct 35 into circuit control passage 20 is cut off. If at this time the inertia forces in the boom are still moving thev boom in its initial direction, and pressure is still high in circuit control passage 19, then fluid is being forced out of motor 25 yet fluid supply to motor 26 has been shut off. to; become slack, and the pressure in circuit control passage 20 drops immediately below the setting of check valve 32. In such case the fluid in transfer passage 29 is under a higher pressure than the fluid in circuit control passage 20, and valve 31 acts as a check valve. In such case fluid enters the valve through ports 61 and passes through seat 62, lifts main valve body 63 off its" At the time this fluid flow through valve 30 be- In such case chain flight 45 tends.

seat, and-flows through ports 64 into circuit control passage 20. Since the displacement of the cylinders of the two fluid motors 25 and 26 is the same, this flow of oil from fluid transfer passage 29 through valve 31 into circuit control passage 20 will prevent cavitation in fluid motor 26, and will prevent the chain flight 45 from becoming slack. This flow will continue until all movement of the boom has ceased and the boom shaft 42 is at rest.

The exact reverse of this operation occurs when valve spool 18 is moved to the right of its neutral position. In such case the valve body 63 of valve 31 serves as a relief valve to allow the escape of fluid under excess pressure in circuit control passage 20 into fluid transfer passage 29, and the valve body 56 of valve 30 acts as a check valve to allow an equal flow of fluid from fluid transfer passage 29 through the valve into circuit control passage 19, to prevent motor 25 from starving of fluid. Having described the invention with sufficient clarity to enable those familiar with this art to construct and use it, I claim:

- 1. In a hydraulic motor actuated mechanism in which a pair of opposed single acting fluid motors have their respective plungers connected to the opposite ends of a taut chain or other similar flexible tension element which is incapable of transmitting a compressive force, and in which said chain is operably associated intermediate its ends with a boom carrying pivot so that when the tension element is pulled in one direction by the plunger of the first motor the boom is swung in one direction about its pivot, and when the tension element is pulled in the opposite direction by the plunger of the second motor the boom is swung in an opposite direction, a control system for said mechanism capable of absorbing the kinetic energy transmitted to the motors by the swinging boom and thereby cushioning the stopping of boom motion, and also capable of preventing cavitation in both fluid motors to thereby maintain tautness in the chain, said control system comprising: fluid supply and return passages; two circuit control passages connected respectively to the two motors and connectible to the fluid supply and fluid return passages; shiftable valve means effective in a neutral position to block the flow of supply fluid to and from both circuit control passages, and shiftable to selectively connect either circuit control passage with the supply passage while directly connecting the other circuit control passage with the fluid return passage, said means also being efiective in intermediate positions to block the flow of fluid from one circuit control passage directly to the fluid return passage while affording limited flow of fluid from the supply passage to the other circuit control passage and its motor; a fluid transfer passage connectible to both said circuit control passages and to the fluid return passage independent of said shiftable valve means; a pressure opened check valve affording flow of fluid from the fluid transfer passage into the fluid return passage; and differential pressure opened means affording flow of fluid only under excess pressure from one circuit control passage through the fluid transfer passage into the other circuit control passage independent of said shiftable valve means for maintaining a positive fluid pressure on the plungers of both motors regardless of the direction of plunger movement.

2. A fluid flow control valve for a pair of opposed single acting fluid motors the plungers of which are connected by a. chain or other flexible work performing tension element which causes them to co-act, said valve comprising: fluid supply and return passages; two circuit control passages connected respectively to the two motors, and connectible to the fluid supply and fluid return passages; shiftable valve means eflective in a neutral position to block the flow of supply fluid to and from both circuit control passages, and shiftable to selectively connect either circuit control passage with the supply passage while directly connecting the other circuit control passage with the fluid return passage, said means also being effective in intermediate positions to block the flow of fluid from one circuit control passage directly to the fluid return passage while affording limited flow of fluid from the supply passage to the other circuit control passage; afluid transfer passage connectible to both said circuit control passages and to the fluid return passage independent of said shiftable valve means; pressure relief valves affording flow of fluid only under excess pressure from the respective circuit control passages into said fluid transfer "passage; a pressure opened check valve affording flow of fluid from the fluid transfer passage into the fluid return passage; and pressure opened check valves respectively afiording flow of fluid from the fluid transfer passage into either circuit control passage when the pressure therein drops below the pressure required to open the first mentioned check valve.

3. In a hydraulic motor actuated mechanism in which a pair of opposed single acting fluid motors have theirrespective plungers connected to the opposite ends of a taut chain or other similar flexible tension element which is incapable of transmitting a compressive force, and in which said chain is operably associated intermediate its ends with a boom carrying pivot so that when the tension element is pulled in one direction by the plunger of the first motor the boom is swung in one direction about its pivot, and whenthe tension element is pulled in the opposite direction by the plunger of the second motor the boom is swung in an opposite direction, a control system for said mechanism capable of absorbing the kinetic energy transmitted to the motors by the swinging boom and thereby cushioning the stopping of boom motion, and also capable of preventing cavitation in both fluid motors to thereby maintain tautness in the chain, said control system comprising: pressure fluid supply and fluid return means; shiftable valve means for selectively connecting a first of said fluid motors with fluid supply means while connecting the second motor to fluid return means to swing the boom, said valve means being shiftable to initiatestoppage of boom movement by blocking flow of return fluid from said second motor while afiording limited flow of supply fluid to said first motor; pressure opened means independent of said shiftable valve means to absorb boom kinetic energy by affording flow of fluid only under excess pressure from said second motor to fluid return means while pressure fluid continues to be supplied to said first motor in limited quantity; and differential pressure opened means independent of said shiftable valve means for preventing cavitation in said first motor by affording flow of fluid to said first motor only when pressure therein drops below normal motor operating pressure.

4. A fluid flow control valve for a pair of opposed single acting fluid motors the plungers of which are connected by a chain or other flexible work performing element which causes them to co-act, said valve comprising: a housing having a bore therein; pressure fluid supply and fluid return means defined by the housing, both communicating with said bore; means in the housing defining two circuit control passages, both communicating with said bore and each connected to a respective one of said motors; shiftable valve means in said bore effective in a neutral position to block fl0W Of fluid between both motors and the fluid supply and fluid return means through the respective circuit control passages, said valve means being shiftable to selectively afford flow of pressure fluid from the fluid supply means through either circuit control passage to its connected motor while simultaneously affording flow of return fluid from the other motor through its connected circuit control passage to the fluid return means, said valve means being shiftable to intermediate positions to block the flow of return fluid from one motor through its connected circuit control passage through the bore to the fluid return means wagon" while affording limited flow 'of'pressure'fluid "from the fluid supply means "through the bore and'the other circuit 'controlpassage'to'the other motor;-'a fluid=tran$fer passage defined-by thehousing; two'pressure reliefvalves in "the housing oriented to aflord flow o'f fluid under excessive-pressure from therespec'tive circuit'control'passages into said fluid transfer'passage independehtbftfie shiftable valve means and its bore; a pressure opened check valve oriented to aflord flow of fluid "from the transfer passage into the fluid returnmeans; and a pair of-pressureopened check valves oriented to afiord flow of 'fluid from theflui'd transfer passage into' the respective circuit control passages only in response to a drop in pressure in either circuit control passage to a valuebelow that required to open the firstmentioned checsk'valve.

"5. "A fluid flow-control valve for a 'pair'of opposed single acting fluid motors the plungers of Whichare connected by a chain or other flexible work performing element which causes them to co-act, said valve-comprising: a housing having a bore therein; pressure fluid supply and fluid return means defined by the housing, both communicating with said bore; meansin the housing defining two circuit control passages; both communicating with said'boreand each connected=to arespective one of said motors; sl1iftable valve means in said bore effective in a ncutralposition tobl'ock flow of fluidbetweenboth motors and the fluid supply' an'd fluid return means through the respective circuit control "passages, said valve means beingshiftable to selectively aifordflow ofpressure fluid from the fluid supply means through either circuit control passage to'its connected motor while simultaneously afiording flow of return fluid'from 'the other motor through its connected circuit-controlpassage to the fluid return means, said valve means being shiftable to intennediate positions to block the "flow of return fluid from one motor through itsconnected circuit controlpassage through the bore to thefluid return means while affording limited flow of pressure fluid from the fluid supply means through the bore and the other circuit control passage to the other motor; a'fluid'trans'fer passage define'd'by thehousing; a'pressure opened'check valve oriented to aflord flow of fluid from said'transfer passage into the fluid "return means; and a pair of "differential "pressureopened two-way flow valves 'each'assoc'iatcd with arespective-one of said circuit controlpassages, 'each or said flow valves being responsive toa pressure above motor-operating pressure'to afford flow of fluidfrom'itsassociated circuit control passageinto saidiluid transfer passage, and each of said two-wayflow valves also being responsive to pressure inits'associated' circuit control passage below motor operating pressure to aflord flowof fluid from said fluid transfer passage into such circuit control passage.

6. A control valve for controlling flow of fluid'toand from a pair-of opposed single acting fluid motors the plungers of which are connected together by aflexible work-performing tension element which causes the plungers 'tomove simultaneously in opposite directions with respect to'their respective cylinders, saidvalve comprising: a housing havinga fluid'supply'passage, a fluidreturn passage,'and'two circuit control passagesincommunication withthe respective cylinders of the two motors; shiftable valve means interposed between the-two circuit control passages and the supply and'return passages, and formed tosialectively connect'the passagesas followsz to connect-the supply passage with either circuit control passage'while connecting the other circuit control passage to the-return passage; tomaintain the connection between either circuit control passage while isolating the No I references cited. 

